FT-Raman spectroscopic analysis of endolithic microbial communities from Beacon sandstone in Victoria Land, Antarctica

Abstract

Laser-based Fourier-Transform Raman spectroscopy (FTRS) has been used to identify in situ compounds of ecophysiological significance in diverse field-fresh Antarctic cryptoendolithic microbial communities. FTRS does not disrupt the community and permits characterization of visible and invisible compounds in their natural configuration within cells and their current or former microhabitat. The small "footprint" of the microscopic laser beam permits accurate analysis of discrete zones of compounds produced by extant or degraded micro-organisms with minimum destruction of the biota. This spatial chemical analysis is applicable to any translucent or exposed habitat or biotic assemblage. Two hydrated forms of biodegradative calcium oxalate were differentiated in black-pigmented and hyaline lichen zones of endolithic communities. The oxalate was restricted to zones containing fungi. Communities dominated by cyanobacteria at Battleship Promontory (77"s) and a newly discovered site at Timber Peak (74"s) contrasted chemically with those dominated by eukaryotic algae at East Beacon (78"s). FTRS also showed the zonation of pigments including chlorophyll and UV-protective carotenoids in situ. At extreme sites on the polar plateau, it revealed the presence of "fossil" endolithics where detrimental climatic changes had made the microbes non-viable or amorphous, being represented solely by their residual bio-molecules. The technique has potential for past or present life-detection anywhere in the world without destruction of the microniche.

Miniaturized Raman instrumentation detects carotenoids in Mars-analogue rocks from the Mojave and Atacama deserts

“…In another case of salinixanthin from S. ruber Raman spectra indicate that there are few structural differences [52]. Other studies also demonstrated in laboratory conditions that benchtop instrumentation is able to detect biomolecules associated with the extremophilic endolithic colonization of rocks [38,[53][54][55][56][57][58][59][60].…”

Biologically–induced elemental variations in Antarctic sandstones: a potential test for Martian micro-organisms

“…The cryptoendolithic habitat is widespread throughout the Beacon Supergroup, extending from Victoria Land through the Transantarctic Mountains, East Antarctica (Russell et al 1998). The samples were collected by a British Antarctic Survey expedition to Terra Nova Bay and McMurdo Base during the Antarctic summer of 1995-1996(Edwards et al 1997, from six different localities (Table 1 and Fig.…”

Astrobiological instrumentation for Mars – the only way is down

“…Inorganic compounds of ecological significance such as UV screening haematite and bio-weathering calcium oxalate have similarly been studied using laser Raman spectroscopy. Calcium oxalate can be detected as evidence of rock bioweathering (Russell et al 1998). The Raman water signature is small so that it is applicable to untreated field-fresh material.…”

“…For studies of Antarctic samples of cryptoendolithic microorganisms, spectra were recorded using a Fourier transform (FT) Bruker IFS66 (Bruker IR Analytische GmbH, Karlsruhe) laboratory instrument and FRA 106 Raman module attachment with 350 mW Nd/YAG laser excitation at 1064 nm and a liquid nitrogen-cooled germanium detector (Russell et al 1998 ;Newton et al 2000). For spectroscopy of rock profiles and surface crusts, this was coupled via a TV camera to a Raman microscope with a r40 objective giving a spot diameter of y40 mm at the sample.…”